Conventional windows and skylights are inserted into walls or roofs of buildings to introduce natural light into the interior of a building to offset the need for artificial light. Existing windows and skylights allow for outside natural light to penetrate to the inside of a building during daylight hours. The color temperature of natural light penetrating through a window or skylight changes over the course of a day, season or due to changes in weather conditions (overcast vs. cloudless sky). Existing windows and skylights, however, do not have the ability to change a color temperature of the natural light entering the interior of a building to a more desired color temperature.
As shown in FIG. 1, a typical building 10 includes a roof 11 exposed to the exterior of the building 10. A ceiling 12 and a room 13 are present within the interior of the building 10. A skylight 15 is positioned in the roof 11 and extends through the building 10 and ceiling 12 to the interior of room 13. The exterior entrance 15′ of the skylight 15 is positioned to receive natural daylight 17 and pass the natural light to the interior of room 13 and thereby supply illumination 15″ the interior of room 13. Similarly, a window 14 is positioned on a side of building 10 for passing natural light to the interior of room 13. Structures of skylights are know. For example, the skylight can be substantially flush with the roofline with a vaulted ceiling. Other skylights extend downward into a room having a drop down ceiling and include a reflective surface to carry light into the room. These are but a few examples of conventional skylight structures.
Consumers typically prefer the daylight of the morning or late afternoon hours, due to the presence of a “warmer” red coloration. A desirable color temperature during a time period in the morning or late afternoon hours is in the range of about 3,000 to 3,500° K depending on local weather conditions. Over the course of the day, the color temperature increases to around 5,600° K at midday depending on local weather conditions. This midday light is characterized as “cooler” light (despite actually having a higher color temperature than morning light) due to the presence of more blue and green colors present in the light. Thus, the higher color temperature of midday light is less preferred by consumers than the lower color temperature of morning light (e.g., near sunrise) or later afternoon (e.g., near sunset).
Hence a need exists for techniques and equipment for color correction of day light that maintains a substantially constant color temperature over a period of time such as the course of a day or season or due to changes in weather conditions, and preferably maintains high lumen intensity at the same time.